Various methods of preparing .beta.-adrenergic blocking agents of the 3-substituted-4-(3-amino-2-hydroxypropoxy)-1,2,5-thiadiazole type are known in the art. Such methods are disclosed in various United States Patents such as U.S. Pat. Nos. 3,657,237; 3,655,663 and 3,619,370.
Novel 1,2,5-thiadiazole aldehydes have been discovered. The aforesaid .beta.-adrenergic blocking agents can be readily prepared from these novel aldehydes.